Free-flowing groundwater cold plunge bath on the shore of Lake Kizaki that can reach single temperatures
Nagano Omachi City
Located on the shore of Lake Kizaki in Omachi City, Nagano Prefecture, Yupuru Kizaki-ko is a spa & resort facility with hot springs and a heated swimming pool. In addition to enjoying hot water drawn from Kuzu Onsen, what has become a topic among sauna enthusiasts is the free-flowing groundwater cold plunge bath. In winter the water temperature can drop to the 7°C range, becoming a "single" (below 10°C), offering an intense cold and exhilarating sensation.
TypeNatural Hot Spring
A simple hot spring (weakly alkaline, hypotonic, high-temperature spring) supplied from the abundant waters of Kuzu Onsen. The water is colorless and clear with no strong odor, and is gentle on the skin.
Sauna TypeDry Sauna
Stove Typeelectric
Capacity8people
An L-shaped dry sauna at approximately 80–95°C. The space is silent with no TV or background music, allowing you to work up a steady sweat in a bright atmosphere with natural light from the windows.
Water QualityNatural Water (Groundwater, Spring, etc.)
Capacity1people
A compact 1–2 person cold plunge bath continuously fed with groundwater from the tap. In winter the water can fall into the 7–9°C range, becoming a "single", and is notable for its intense cold.
Closed Days: Thursday
10639-1 Taira, Omachi City, Nagano 398-0001, Japan
Gender Access
Gender Separated
Curated by an expert who visits onsen and sauna facilities every day and has explored 300+ locations — only facilities confirmed to be truly exceptional are featured.
Learn more
Free-flowing groundwater cold plunge bath on the shore of Lake Kizaki that can reach single temperatures
Nagano Omachi City
Located on the shore of Lake Kizaki in Omachi City, Nagano Prefecture, Yupuru Kizaki-ko is a spa & resort facility with hot springs and a heated swimming pool. In addition to enjoying hot water drawn from Kuzu Onsen, what has become a topic among sauna enthusiasts is the free-flowing groundwater cold plunge bath. In winter the water temperature can drop to the 7°C range, becoming a "single" (below 10°C), offering an intense cold and exhilarating sensation.
TypeNatural Hot Spring
A simple hot spring (weakly alkaline, hypotonic, high-temperature spring) supplied from the abundant waters of Kuzu Onsen. The water is colorless and clear with no strong odor, and is gentle on the skin.
Sauna TypeDry Sauna
Stove Typeelectric
Capacity8people
An L-shaped dry sauna at approximately 80–95°C. The space is silent with no TV or background music, allowing you to work up a steady sweat in a bright atmosphere with natural light from the windows.
Water QualityNatural Water (Groundwater, Spring, etc.)
Capacity1people
A compact 1–2 person cold plunge bath continuously fed with groundwater from the tap. In winter the water can fall into the 7–9°C range, becoming a "single", and is notable for its intense cold.
Closed Days: Thursday
10639-1 Taira, Omachi City, Nagano 398-0001, Japan
Gender Access
Gender Separated
Curated by an expert who visits onsen and sauna facilities every day and has explored 300+ locations — only facilities confirmed to be truly exceptional are featured.
Learn more